Extracting data from Polynomial regression equation

[dunlop407703]

Hi all,

Apologies if this question seams disjointed but I am having trouble organising my thoughts. I've decided just to put what I can into words a hope someone can help.

I have a cumulative data set as follows. I have graphed this data and created a 3rd order polynomial regression equation to allow myself to accurately predict data.

	6.35 x 0.15
Density	Cum Ash	Cum Yield
1.30	3.18	20.32
1.35	4.89	32.01
1.40	6.21	37.58
1.45	7.40	41.48
1.50	9.02	45.70
1.60	13.62	55.80
1.70	16.48	62.29
1.80	19.93	69.47
2.00	25.36	79.77
2.20	38.11	100.00

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From my regression equation I can predict the 'Cum Yield' at an input 'Cum Ash' (x). What I would like to do is be able to calculate the new cumulative results after I remove a fraction from the data. For example if set 'Cum Ash' to 10%, the 'Cum Yield' is returned at 48.22%, based on that outcome I would then like to be able to say "given that I've removed the material up to a 10% cut off, how much of the remaining material do I need to get a sample at 30%".

Any input will be greatly appreciated.

Thanks